JP2004092650A - Improved method of manufacturing rotor of centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a rotor (10) of a centrifugal compressor produced from an integral structured disk at low cost, allowing obtaining the optimal dimensional accuracy meeting a corresponding expectation value. <P>SOLUTION: A disk has a radial cavity (12) formed within a rotor (10) by processing the disk in a radial direction in a manner to remove chip using at least a tool (29) of a value-controlling device. Since there is no distortion caused by welding, the optimal dimensional accuracy meeting design requirements can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an improved method for manufacturing a rotor of a centrifugal compressor.

The term centrifugal compressor typically uses one or more rotors or impellers to impart the necessary energy to the fluid to change the pressure, so that the compressive fluid is greater than the pressure at which the fluid was received. It defines a machine that returns with pressure.

Each rotor includes a number of blades arranged radially to form a number of passages converging towards the center of the rotor;

Centrifugal compressors, especially high pressure type centrifugal compressors, usually have a rotor which is three-dimensionally tested in a known manner.

More specifically, the main components of these rotors for centrifugal compressors are hubs, shrouds and blades.

Due to the high concentration of gas, a truly important problem in the technical field of compressors, especially high-pressure type compressors, is to ensure the stability of the rotor.

合成 The resultant force, which is proportional to the concentration of the gas and is generated by the labyrinth of the gas, can cause unacceptable subharmonic oscillations that have a detrimental effect on the rotor.

In fact, the sensitivity of the rotor to these forces increases more or less proportionally with the flexibility of the rotor.

In addition, the overall dynamic performance of the rotor is particularly important for this type of application, as it increases the stiffness of the rotor under the same operating conditions (ie, having the same bearing, the same temperature, the same gas pressure, etc.). The simplest way to increase is to use a shaft with a large diameter.

Accordingly, in the prior art, the diameter of both the shaft and the hub is increased to increase stiffness and insensitivity to disturbances, and thus to enhance the inherent rotational dynamic performance of the centrifugal compressor at high pressure. It has been.

Thus, the aerodynamic passage is obtained directly on the shaft, since the spacer has been eliminated.

More specifically, the two rings are kept axially positioned, the front ring is made of two parts and the rear ring is made of a single part. In addition, a coating of a material having a high level of hardness protects the shaft.

These features ensure that the aerodynamic passage is not altered and also mean that this arrangement is particularly effective in increasing the stiffness of the shaft. However, these changes mean that different techniques have to be taken into account for the manufacture of these rotors for centrifugal compressors.

With specific reference to the prior art, it should be noted that in conventional methods, the blade is obtained by milling the hub, followed by welding from inside the opening to join the parts.

Another technique is used for rotors with low flow coefficients, but in that case the opening is too narrow to allow welding from within. In this technique, the two parts are welded from the shroud side.

It will therefore be seen that after the welding has been performed, it is necessary to perform further heat treatments used to reduce the residual tension formed.

It is therefore an object of the present invention to improve the above-mentioned technique, in particular an improved method of manufacturing a rotor of a centrifugal compressor, which makes it possible to obtain an optimum dimensional accuracy consistent with the corresponding expected values. It is to present.

Another object of the present invention is to provide an improved method of manufacturing a rotor of a centrifugal compressor, which makes it possible to obtain an impeller having a high level of structural strength.

It is another object of the present invention to provide an improved method of manufacturing a rotor of a centrifugal compressor, which is particularly reliable, simple and functional, and at a low cost compared to the costs of the known art. It is.

These and other objects according to the present invention are achieved by providing an improved method of manufacturing a rotor of a centrifugal compressor as claimed in claim 1.

Additional features of the improved method of manufacturing a rotor of a centrifugal compressor are set forth in the following claims.

Advantageously, the improved method of manufacturing the rotor of a centrifugal compressor according to the invention results in a rotor with no structural breaks.

Furthermore, it becomes possible to manufacture a rotor having very good mechanical properties.

The machining of aerodynamic surfaces has the advantage that it is performed by automatic machining and thus avoids any manual intervention.

Furthermore, according to the improved manufacturing method of the rotor of the centrifugal compressor according to the present invention, since there is no distortion caused by welding, an optimum dimensional accuracy according to design requirements can be obtained.

表面 The surface quality obtained is very good, virtually free of defects and has optimal aerodynamic efficiency.

Eliminating welding operations can save up to 70% of the cycle time required to manufacture the impeller.

Note that a more regular surface results in easier balancing.

All of these advantages are particularly pronounced in high pressure re-injection machines where detrimental periodic forces can occur due to the high pressure and concentration of gas. By using the method according to the invention, there is no longer any metallurgical interruption in the interior of the rotor, which leads to a decisive reduction of these forces.

Ultimately, the welding used in the prior art produces distortions that result in variations of 5% or more in the width of the rotor blades, especially in the case of impellers with low flow rates. In contrast, the method according to the invention guarantees a processing accuracy of 1% or 2%.

The features and advantages of the improved method of manufacturing a rotor of a centrifugal compressor according to the present invention will become more clear and more apparent from the following description made by way of non-limiting example with reference to the accompanying schematic drawings. Will.

The method according to the invention will now be described with specific reference to the relevant figures.

To manufacture a rotor, generally designated 10, by the method of the present invention, the starting point is a monolithic disc, usually made of steel.

Next, processing is performed using a numerical control machine.

In recent years, the tools used on these machines with multiple controlled axes have been able to significantly enhance their ability to remove metallic materials, and they also perform various types of machining. Reduce the set time due to the fact that you can. In addition, these modern tools allow machining of particularly complex forms.

For example, some did not take into account the fact that in the past three different settings were required as a result of the development of modern control software, but until recently three separate tools were required. With a tool, the workpiece can be milled, bent and drilled with a single setting.

FIG. 1 shows how a monolithic disc is machined radially by a tool 20 starting from the outer diameter and forming the outer part of the cavity.

The tool 20 advances while performing a continuous terrace forming process, and processes until the tool reaches an intermediate depth with respect to the full width of the circular ring of the monolithic disc.

FIG. 2 shows how the monolithic disc is machined radially by the tool 20, starting from the inner diameter.

The tool 20 moves forward with continuous terrace machining until it reaches the already formed outer cavity and thus forms the required radial cavity 12.

FIGS. 3 and 4 show a tool 20 forming a radial cavity 12 of this type.

It is clear that the invention also relates to a monolithic disc which is first machined from the inside and then machined from the outside. In many cases, two machining operations are performed simultaneously using two tools located on two controlled axes of one or more numerically controlled machines.

The shaping of each radial cavity 12 takes place in two separate stages, the first stage starting from the outer diameter and progressing to the furthest position that can be reached inside the disc, and the second stage It is emphasized that it is advantageous to complete the duct to be formed by machining starting from the inner diameter, i.e. from the area near the inlet edge of the rotor 10, and proceeding outward.

It is also useful to note that prior to the two steps, a preliminary step is performed to determine the feasibility of the machining. In other words, it must be possible to determine whether the two stages will be superimposed and whether the required tool 20 is available (determined by evaluating the dimensions of the tool).

If one or both of these conditions do not exist, an anomaly is indicated, which interrupts the machining plan.

Thus, it must be possible to use more than one assembly of tools 20 during machining, starting from the shortest, but this shortest also falls within the available set of tools 20. Will be the first tool to be inserted into the tool.

The diameter of the tool 20 to be used must be chosen according to the radius at the joint of the blade base.

The technique of removing shavings is a technique of the kind known as pockets (based on the processing performed, starting from the center and continuing toward the outer diameter) and is obtained by a continuous terrace forming operation. The depth must be such that it corresponds to the tool 20 selected and to the level of finish obtained. For this reason, during the preparation phase, these data are entered as variables.

With a single inclination of the axis of the tool 20 until the maximum depth is obtained, and also with the possibility of machining by undercut by the design of the tool 20, the first stage of so-called pocketing must be performed. Later, a command that causes the tool 20 to assume a different tilt must be transmitted to the axis.

方法 This method makes it possible to obtain a greater depth.

Advantageously, this increase in tilt is performed by a numerically controlled machine having five controlled axes.

幾 つ か If several repositioning operations are required to complete the cavity, the operations are performed continuously until the maximum possible depth is reached.

The overall dimensions of the tool 20 must be taken into account in order to prevent interference between the finished surface and the dimensions constituted by the outer contour. The overall dimensions of the tool holder must also be checked to ensure that the tool holder does not collide with any surface.

For this purpose, in most cases where the machining is being carried out externally, the vibration of the axis of the tool 20 will always occur in the negative direction, so that the mandrel support, even within the dimensions considered, And the dimensions of the turntable must be taken into account.

注目 Note that this method uses a tool 20 of all known types.

It can be seen that after processing to remove the swarf has been performed, the impeller can be heat treated, and then the steps of rotor dimensional inspection, balance inspection, and dynamic inspection will be performed. Would.

The foregoing description has characterized the improved method of manufacturing a rotor of a centrifugal compressor according to the present invention and has identified corresponding advantages.

The following closing considerations and comments are now provided to more accurately and clearly state their benefits.

Firstly, it can be seen that in the method according to the invention there are no structural cuts on the rotor.

上 On top of that, please remember the following:

・ The mechanical properties of the rotor are very good.

The aerodynamic surface can be machined by automatic machining, thus avoiding any manual intervention.

・ Because there is no distortion caused by welding, the optimum dimensional accuracy is obtained according to the design requirements.

The surface quality is extremely good, virtually free of defects and has optimal aerodynamic efficiency.

Reduce cycle time for impeller manufacturing by up to 70% by eliminating welding operations.

・ Because a more regular surface is obtained, the balancing work becomes easier.

All of these benefits are particularly important in high pressure re-injection machines.

In fact, the high pressures and concentrations of gas generated in these machines can generate pressure pulses related to imbalance in the aerodynamic region, especially in the exhaust flow path, and these pulses can cause harmful effects. Periodic force is generated.

By using the method according to the invention, there is no longer any metallurgical break inside the rotor, which is a significant advance in eliminating this kind of problem.

Moreover, the welding used in the prior art produces distortions which can lead to fluctuations of the rotor blade width of 5% or more, especially in the case of impellers having low flow rates.
In contrast, the method according to the invention guarantees a processing accuracy of 1% or 2%, which allows an optimal match between the planned performance level and the achieved performance level.

Finally, many other modifications may be made to the improved method of manufacturing the rotor of a centrifugal compressor without departing from the principles of novelty inherent in the inventive concept. Clearly what you can do.

It is clear that in practical implementations of the invention, any materials, dimensions and forms can be used, if necessary, and can be replaced by others which are technically equivalent.

The reference numerals described in the claims are for easy understanding and do not limit the technical scope of the invention to the embodiments.

1 is a perspective view of a rotor of a centrifugal compressor, showing a tool working from the outer diameter of the rotor itself according to the method of the invention. 1 is a perspective view of a rotor of a centrifugal compressor, showing a tool working from the inner diameter of the rotor itself according to the method of the invention. FIG. 4 is a cross-sectional plan view of a portion of a rotor showing a tool working from the inner and outer diameters of the rotor itself in accordance with the method of the present invention. FIG. 4 is a side cross-sectional view of a portion of a rotor showing a tool working from the top plane and the outer diameter of the rotor itself in accordance with the method of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 10 Rotor 12 Radial cavity 20 Tool

Claims (21)

An improved method of manufacturing a rotor (10) of a centrifugal compressor manufactured from a monolithic disc, the disc being removed by at least one tool (20) of a numerical control machine. An improved method characterized by processing radially to form a radial cavity (12) in the rotor (10). Method according to claim 1, characterized in that the first tool (20) works starting from the outer diameter of the disc until the outer part of the radial cavity (12) is formed. . The first tool (20) is advanced with a continuous terrace forming operation and works until reaching an intermediate depth with respect to the full width of the circular ring of the monolithic disc. 3. The improved method according to 2. Starting from the inner diameter of the disk, machining a second tool (20) until the second tool reaches the outer cavity and thus completes the radial cavity (12). 4. The method of claim 3, wherein Method according to claim 4, characterized in that the first tool (20) and the second tool (20) are identical tools (20) of the numerical control machine. The first tool (20) and the second tool (20) may be machined simultaneously with the tools (20) arranged on two axes controlled by at least one numerically controlled machine. The method according to claim 4, characterized in that it is characterized by: Method according to claim 1, characterized in that a second tool (20) works from the inner diameter of the disc until an inner part of the radial cavity (12) is formed. The second tool (20) is advanced with a continuous terrace forming operation and works until reaching an intermediate depth relative to the full width of the circular ring of the monolithic disc. 8. The improved method according to 7. A first tool (20) starting from the outer diameter of the disc and working until the first tool reaches the inner cavity and thus completes the radial cavity (12). The improved method according to claim 8, wherein Method according to claim 9, characterized in that the first tool (20) and the second tool (20) are identical tools (20) of the numerical control machine. Before machining with the tool (20), a preliminary step is performed to determine the feasibility of the machining, i.e. to check whether there is a superposition of the tool (20) during the machining. 7. The method according to claim 6, wherein the following is performed. 12. The improvement method according to claim 11, wherein when the superimposition is present, an abnormality is indicated, whereby the machining plan is interrupted. Method according to claim 1, characterized in that the tool (20) is started with the shortest available tool and is used continuously. Method according to claim 1, characterized in that the diameter of the tool (20) is selected according to the radius of the joint at the blade base. The method according to claim 1, wherein the process for removing shavings is a type of process known by the name of a pocket. The so-called pocket of the first stage, which is performed using a single inclination of the axis of the tool (20) until the maximum depth is reached, and also with the possibility of machining by undercut according to the design of the tool (20). A method according to claim 15, characterized in that, after forming, a command causing the tool (20) to assume a different inclination is transmitted to the shaft. 17. The method of claim 16, wherein the different tilts are performed by a numerically controlled machine having five controlled axes. 2. The method according to claim 1, wherein the rotor (10) is subjected to a heat treatment after the machining for removing shavings. 19. Method according to claim 18, characterized in that the heat treatment is followed by dimensional, balancing and dynamic inspection steps of the rotor (10). Method according to claim 1, characterized in that the rotor (10) is made of steel. An improved method of manufacturing a rotor (10) of a centrifugal compressor, substantially all as described and claimed and for the specified purpose.

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